Two-temperature refrigerating system



2 Sheets-Sheet l Dec. l1, 1956 R. w. DoEG TWO-TEMPERATURE REFRIGERATING SYSTEM Filed June 23, 1953 Dec. 11, 1956 RW, DQEG 2,773,355

TWO-TEMPERATURE REFRGERATING SYSTEM Filed June 25, 1953 2 Sheelzs-Shee-tl 2 Han? INVEN TOR. @aU-'w W1' Do /50 /60 BY if e, mm,

TTORNEY United States Patent O TWO-TEMPERATURE REFRIGERATING SYSTEM Ralph W. Doeg, Detroit, Mich., assignor to Nash- Kelvinator Corporation, Detroit, Mich., a corporation of Maryland Application June 23, 1953, Serial No. 363,460

3 Claims. (Cl. 62-3) The present invention relates to refrigerating apparatus yand more particularly to refrigerators of the two temperature type.

One of the objects of the present invention is to provide within a refrigerator cabinet an improved arrangement of maintaining at a constant pressure and temperature one evaporating section of a refrigerating system utilizing one or more refrigerant evaporating sections connected in series circuit relationship.

Another object of the present invention is to provide an improved two temperature type refrigerating system wherein the low temperature evaporator is controlled by thermostatic means associated therewith and the high temperature evaporator is controlled at a constant temperature and pressure by a pressure responsive valve positioned in series circuit relationship between said evaporators.

It is another object of the present invention to provide a pressure responsive valve that, when placed between two evaporating sections,.will maintain one of said sections at a constant relatively higher temperature and pressure and provide an outlet for gaseous refrigerant 2,773,355 Patented Dec. 11, 1956 lower pressure evaporating section which prevents the pressure from rising above a certain value in the higher pressure section. Control of the refrigerating system consists of a thermostat which is responsive to changes in temperature in the lower temperature evaporating section. By utilizing a positive acting valve a constant pressure is maintained. In the use of a xed restriction between two evaporating sections a pressure difference is maintained between the two sections, however the higher temperature section may be reduced to an undesired low temperature especially when the system is controlled by a thermostat responsive to changes in terneprature of the low temperature evaporating section. Under such circumstances the user may desire fast freezing and set the thermostat for such and the result is that some of the food stored in the food storage compartment becomes frozen. By the present arrangement as herein specifically disclosed such undesirable condition. is prevented.

Shown in the drawings is a refrigerator cabinet 20 formed with an outer sheet metal casing 22 and an inner sheet metal liner 24 between which is interposed suitable heat insulating material 26. The outer sheet metal casing is extended so as to provide a machine compartment 27. The inner `sheet metal liner forms by its inner walls thereof a food storage compartment which is insulated from the machine compartment by insulating material 32.

A door 34 is provided for closing the opening 'to the i food `storage compartment, and a closure member 36 for to be returned to one cylinder of a two cylinder compressor to enable the compressor to operate at the high back pressure existing in the higher temperature evaporator.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the invention is clearly shown.

In the drawings: j

Fig. 1 is a side view with parts broken away and parts shown in cross-section of a refrigerator cabinet embodying features of the present invention;

Fig. 2 is a diagrammatic illustration of a refrigerating system and the relief valve employed thereinembodying features of my invention.

In accordance with my invention I provide a refrigerating system which includes two evaporating sections connecting in series circuit relationship. Between the two sections is a pressure responsive valve which is actuated by the pressure existing in evaporating` section which is the first to receive liquid refrigerant. This valve maintains the temperature in the evaporating section which is the rst to receive refrigerant at a consant relatively higher pressure and relatively higher temperature due to the fact that a two cylinder motor-compressor unit is utilized for withdrawing gaseous refrigerant from the two evaporating sections. The cylinder which is utilized for withdrawing gaseous refrigerant from the evaporating section which operates at the higher pressure is of such small displacement that it never can reduce the pressure in that section below a certain value as the cylinder does not have capacity to reduce the pressure so that an undesired low temperature could prevail in the higher pressure section. When the pressure in the high pressure section is at a certain high value, the valve opens to permit liquid and some gaseous refrigerant to flow to the closing the opening to the machine compartment. The closure member 36 is provided with a. vegetable bin 37 projecting into the machine compartment having an inclined rear wall to which is secured an insulated pad 39.

Positioned within the food storage compartment is an evaporating element 40 of any of the well known constructions now in use. The refrigerant evaporating element 40 forms on its inner walls thereof a freezing compartment. The freezing compartment is sealed from the rest of the food storage compartment by a closure mem- `ber 42 and insulated therefrom by an insulated baffle 44 positioned thereunder. The evaporating element 4t) is spaced from the walls of the liner 24 so as to provide a xed path for air circulation in front, on top and behind the element.

Positioned within the food storage compartment are a plurality of vertically spaced shelves 60, 62 and 64. The shelves are preferably constructed of transparent imperforate shelf structures. Angular metal strips 65 are provided along the front edges of the shelves so as to prevent breakage by contact therewith upon placing food stuls `in the refrigerator. These shelves extend substantially from one side of the liner to the other and from substantially the front part of the food compartment to a point adjacent to the rear wall of the liner thereby providing a space 69 for limited air circulation therethrough. The front edge of shelf 64 is spaced from the front of the cabinet to provide space for doors 74. The doors serve to close the lower portion of the cabinet extending from shelf 62 to the bottom wall of the liner. The shelf 64 and doors 74 provide what is herein termed high humidity compartment 77 that includes the space above as well as below shelf 64.

In order to cool the high humidity compartment 77 there is provided a high temperature evaporating section 82 which is bonded to the rear Wall of liner 22 and is adapted to absorb heat through the walls thereof Without the collection of frost thereon at least part of the time. If frost should form thereon it would melt during the on" phase of the refrigerating cycle.

Liquid refrigerant is delivered to the evaporating element 82 by a refrigerant liquifying and condensing element 84 disposed within the machine compartment 27.

The element includes a two cylinder motor compressor 85 having a small cylinder 87 and a large cylinder 88 and condenser 90 secured 'to and carried by base 92` The vdischarge ports of 'cylinders 83 and 87 discharge compressed refrigerant into a common muffler i) whence it is delivered to the refrigerant l'iquifying and condensing element 9d. The condensingI element 90 delivers liquid refrigerant to the 'evaporating element 82 through a small diameter Aof lcapillary tube ltlZ. Liquid and gaseous refrigerant then passes into a relief valve designated in general bythe numeral 120. A vapor return conduit 130 connects the upper portion of the casing 121 of valve 120 to the interior 0f the motor-compressor shell 132. The action 'of `the 4cylinder 87 partially evacuates the valve 120 but since it is of small displacement it cannot at any time reduce the pressure in evaporator 82 below a certain value and at a certain pressure therein the valve proper 132i of valve 120 is opened to permit liquid and lsome gaseous refrigerant to pass through the outlet port 137, through conduit l5@ and into the evaporating element 40. By this arrangement a lconstant pressure and temperature is maintained within the evaporator 32. vGraseous refrigerant is withdrawn from the evaporator lll through vapor return conduit 16th directly to the intake por-t of the larger cylinder 38. Any desired temperature may be maintained by varying the effectiveness of spring 162 within the bellows 164 by rotating the adjusting screw 165.

Since a portion of the refrigerant is evacuated from valve 12.0 yinto the small cylinder 87 a more efficient system is produced since the refrigerant withdrawn will be of high pressure, thus enabling the compressor to` operate at the highest back pressure existing in the system.

Since it is possible at times for a considerable amount of liquid refrigerant to collect in valve 120 the vapor return conduit is connected at the upper portion of the valve thereby forming an accumulator that `will prevent the return of liquid refrigerant to the motor-'compressor.

While I have shown and described the preferred form of the invention, l do not wish to limit myself -to 'the precise details as shown and described, but Wish to avail myself of such variations and modifications as may come within the scope of the appended claims.

I claim:

l. Refrigerating apparatus comprising, a refrigerant evaporator to function at 'a low temperature, a refrigerant compressor having a cylinder operatively connected to said evaporator having a relatively high capacity corresponding to the low temperature to be maintained by said evaporator, a refrigerant condenser operatively connected to the outlet of -said compressor cylinder, a second refrigerant evaporator operatively connected to said condenser to receive liquid refrigerant therefrom, said compressor having a second cylinder operatively connected to said condenser and to said second evaporator, said second compressor cylinder having a capacity less than said first compressor cylinder and being in parallel circuit relationship therewith, and a pressure responsive valve connecting said evaporators in series circuit relationship to maintain the pressure in said second evaporator above a certain value and also connecting said second evaporator directly to said low capacity compressor cylinder.

2. Refrigerating apparatus comprising, a refrigerant evaporator to function at 'a high temperature, a second refrigerant evaporator in series communication with said tirst evaporator and to function at a lower temperature than said first evaporator, a condenser delivering .liquid refrigerant to said first evaporator, a pressure responsive valve controlling liow of liquid refrigerant from said first evaporator .to said second evaporator in response to pressure in said first evaporator to maintain the temperature of said first evaporator substantially constant, a refrigerant compressor having a cylinder operatively connected to said condenser and withdrawing vaporous refrigerant from said second evaporator, lsaid compressor cylinder having a high capacity Icorresponding to the low 'temperature second evaporator, and said compressor having a cylinder of lower capacity than said first compressor cylinder corresponding to the lhigh pressure to be vmaintained in said first evaporator, said second compressor cylinder being operatively connected to said first evaporator between said first evaporator and said valve to withdraw vaporous refrigerant from said first evaporator.

3. Refrigerating apparatus comprising, a refrigerant evaporator to function at high temperature, a second refrigerant evaporator to function at a lower temperature than said first evaporator, a condenser delivering liquid refrigerant to said first evaporator, a refrigerant compressor having a cylinder of high capacity corresponding to the low temperature to Abe maintained by said second evaporator operatively connected thereto and to said condenser, a refrigerant accumulato1intcrposed between and communicating with said evaporators having a liquid refrigerant chamber and a space thereabove lfor separation of vaporous refrigerant 'from 'the liquid, a pressure responsive valve within said accumula'tor controlling liow of liquid refrigerant therefrom to said second evaporator, said valve responding `to the refrigerant vapor pressure within said :accumulator to maintain said 'first evaporator at a substantially constant temperature, and said refrigerant 'compressor having a second cylinder operatively connected to said condenser and to Asaid vapor collecting 'space having a capacity lower than said first compressor cylinder corresponding to the lower temperature to be maintained by the first evaporator.

References 'Cited inthe file of kthis patent UNITED STATES PATENTS 1,779,409 Chilton rOCt. 28, 1930 2,028,735 Hunt Jan. '.2-1, 1936 2,081,883 Philipp fMay 25., 11937 2,240,284 Buchanan Apr. 29 1941 

